`
https://leetcode.cn/problems/find-the-difference/
`

/**
 * @param {string} s
 * @param {string} t
 * @return {character}
 */
var findTheDifference = function (s, t) {
  let res = 0;
  for (let c of s) {
    res = res ^ c.charCodeAt(0);
  }
  for (let d of t) {
    res = res ^ d.charCodeAt(0);
  }

  // 根据异或运算规则，所有字符的异或结果就是多出来的那个字符
  return String.fromCharCode(res);
};